A number of methods of composite sorbents manufacturing on the basis of transition metal hexacyanoferrates is known.
The method in which organic polymer supporting material is treated alternately with inorganic acid and concentrated solution of copper salts and transition metal hexacyanorerrate is known. Three-four washings with the water is to be made in this method that results in forming of the large quantity of toxic wastes and great losses or the important initial materials. Sorbent produced by this method is not able to absorb strontium's ions (USSR, No. 778780BOIj 19/04, 1980).
Also it's known the method in which the supporting material, preliminary saturated with a salt of transition metal during the heating, then dried, and after that treated by saturated solution of potassium hexacyanoferrate during the heating, washed and dried again. It takes a lot of time to complete all works with the hot solutions and as a result the great quantity of liquid toxic wastes appears to be. (USSR, No. 801871BOIj 20/02, 1981).
The sorbents produced by these methods are not sufficiently effective, especially regarding to the recovery efficiency of cesium and strontium from solutions. Moreover, they have high degree of peptization in aqueous medium.
Another known method of the sorbent manufacturing is based on transition metal hexacyanoferrate and the porous supporting materials (U.S. Pat. No. 4,448,711, BOIj 27/24, 1984). In this method the porous supporting material is dipped in the solution of transition metal salt, then this supporting material is treated with aqueous solution of potassium hexacyanoferrate and after that is aged at different temperatures in the aqueous solution of high concentration sodium sulphate.
It takes a lot of time to carry out this method and a great volume of water for washing. The sorbents produced by this method have low specificity to strontium ions and significant peptization in the aqueous medium.
There are known some similar methods, one of them (USSR, No. 1012969BOIj 20/00, 1983) offers to treat the mixture of alkaline metal and transition metal hexacyanoferrates by the solution or polyvinylchloride (PVC) resin in acetone with the subsequent distillation of the latter. In other method (EP, No. 217143, BOIj 39/02, 1983) of the composite sorbent manufacturing the powder of transition metal hexacyanoferrate has been added to the reaction mixture during the process of polycondensation of phenolformaldehyde matrix and then slowly dispersed in the hot oil. Both of above mentioned methods are technologically complicated, ecologically hazardous and have one disadvantage that in the beginning it's necessary to produce, to dry, to grind and to sieve transition metal hexacyanoferrate.
The most close to the object of this invention, regarding to technical essence and the result achieved, is the method of hexacyanoferrate sorbent manufacturing that incorporates the porous supporting material (coal, wood, etc.) treatment with fresh prepared mixture of solutions 90 g/l of potassium hexacyanoferrate (3+) with 145 g/l of iron nitrate (3+) in equal volumes. After the treatment of the supporting, material with the above mixture, the produced substance is washed by water. This procedure is to be repeated 3-5 times. (Chemistry and Technology of Inorganic Sorbents. Intercollege Scientific Transactions. Polytechnic Institute of Permj, 1979pp. 71-74). Taking into account all positive subjects of this method it should be mentioned that recovery efficiency of produced sorbents to cesium ions doesn't excess 85; the method requires the great amount of reagents resulting in low yield efficiency of the finished product (For the triple treatment of one liter of sorbent more than 400g of potassium hexacyanoferrate and 650 g of iron nitrate are consumed); the volume of liquid wastes is significant (Up to 10 liters of industrial water containing one g/l of iron hexacyanoferrate and 10 g/l of potassium nitrate are formed after the treatment of one liter of sorbent); the sorbent produced by this method has low stability in aqueous solutions (7,2%). Moreover, this sorbent doesn't extract strontium ions.